Robotic interventional systems and devices are well suited for use in performing minimally invasive medical procedures as opposed to conventional procedures that involve opening the patient's body to permit the surgeon's hands to access internal organs. Traditionally, surgery utilizing conventional procedures meant significant pain, long recovery times, lengthy work absences, and visible scarring. However, advances in technology have led to significant changes in the field of medical surgery such that less invasive surgical procedures are increasingly popular, in particular, minimally invasive surgery (MIS). A “minimally invasive medical procedure” is generally considered a procedure that is performed by entering the body through the skin, a body cavity, or an anatomical opening utilizing small incisions rather than larger, more invasive open incisions in the body.
Various medical procedures are considered to be minimally invasive including, for example, mitral and tricuspid valve procedures, patent formen ovale, atrial septal defect surgery, colon and rectal surgery, laparoscopic appendectomy, laparoscopic esophagectomy, laparoscopic hysterectomies, carotid angiopiasty, vertebroplasty, endoscopic sinus surgery, thoracic surgery, donor nephrectomy, hypodermic injection, air-pressure injection, subdermal implants, endoscopy, percutaneous surgery, laparoscopic surgery, arthroscopic surgery, cryosurgery, microsurgery, biopsies, videoscope procedures, keyhole surgery, endovascular surgery, coronary catheterization, permanent spinal and brain electrodes, stereotactic surgery, and radioactivity-based medical imaging methods. With MIS, it is possible to achieve less operative trauma for the patient, reduced hospitalization time, less pain and scarring, reduced incidence of complications related to surgical trauma, lower costs, and a speedier recovery.
Special medical equipment may be used to perform MIS procedures. Typically, a surgeon inserts small tubes or ports into a patient and uses endoscopes or laparoscopes having a fiber optic camera, light source, or miniaturized surgical instruments. Without a traditional large and invasive incision, the surgeon is not able to see directly into the patient. Thus, the video camera serves as the surgeon's eyes. Images of the body interior are transmitted to an external video monitor to allow a surgeon to analyze the images, make a diagnosis, visually identify internal features, and perform surgical procedures based on the images presented on the monitor.
MIS procedures may involve minor surgery as well as more complex operations. Such operations may involve robotic and computer technologies, which have led to improved visual magnification, electromechanical stabilization and reduced number of incisions. The integration of robotic technologies with surgeon skill into surgical robotics enables surgeons to perform surgical procedures in new and more effective ways.
Although MIS techniques have advanced, physical limitations of certain types of medical equipment still have shortcomings and can be improved. For example, during a MIS procedure, catheters (e.g., a sheath catheter, a guide catheter, an ablation catheter, etc.), endoscopes or laparoscopes may be inserted into a body cavity duct or vessel. A catheter is an elongated tube that may, for example, allow for drainage or injection of fluids or provide a path for delivery of working or surgical instruments to a surgical or treatment site. In known robotic instrument systems, however, the ability to control and manipulate system components such as catheters and associated working instruments may be limited due, in part, to a surgeon not having direct access to the target site and not being able to directly handle or control the working instrument at the target site.
More particularly, MIS diagnostic and interventional operations require the surgeon to remotely approach and address the operation or target site by using instruments that are guided, manipulated and advanced through a natural body orifice such as a blood vessel, esophagus, trachea, small intestine, large intestine, urethra, or a small incision in the body of the patient. In some situations, the surgeon may approach the target site through both a natural body orifice as well as a small incision in the body.
For example, one or more catheters and other surgical instruments used to treat cardiac arrhythmias such as atrial fibrillation (AF), are inserted through an incision at the femoral vein near the thigh or pelvic region of the patient, which is at some distance away from the operation or target site. In this example, the operation or target site for performing cardiac ablation is in the left atrium of the heart. Catheters are guided (e.g., by a guide wire, etc.) manipulated, and advanced toward the target site by way of the femoral vein to the inferior vena cava into the right atrium through the interatrial septum to the left atrium of the heart. The catheters may be used to apply cardiac ablation therapy to the left atrium of the heart to restore normal heart function.
However, controlling one or more catheters that are advanced through naturally-occurring pathways such as blood vessels or other lumens via surgically-created wounds of minimal size, or both, can be a difficult task. Remotely controlling distal portions of one or more catheters to precisely position system components to treat tissue that may lie deep within a patient, e.g., the left atrium of the heart, can also be difficult. These difficulties are due in part to limited control of movement and articulation of system components, associated limitations on imaging and diagnosis of target tissue, and limited abilities and difficulties of accurately determining the shape and/or position of system components and distal portions thereof within the patient. These limitations can complicate or limit the effectiveness of surgical procedures performed using minimally invasive robotic instrument systems.
For example, referring to FIG. 1, a typical field of view or display 10 of a catheter includes a representation 12 of a catheter and an image 14 of a catheter. The catheter representation 12 is in the form of “cartoon object” that is created based on a position of the catheter determined according to a kinematics model. The image 14 is generated using an imaging modality such as fluoroscopy.
A kinematics model is related to the motion and shape of an instrument, without consideration of forces on the instrument that bring about that motion. In other words, a kinematics model is based on geometric parameters and how a position of the instrument changes relative to a pre-determined or reference position or set of coordinates. One example of a kinematics model that may be used in non-invasive robotic applications receives as an input a desired or selected position of the instrument, e.g., a position of a distal portion of the instrument within a portion of the heart, and outputs a corresponding shape or configuration of the instrument, e.g., with reference to a current or known shape or configuration, that results in positioning of the instrument according to the input.
A fluoroscopic system may be utilized to image, or “visualize”, the elongate instrument or a portion thereof. A drawback of known fluoroscopic imaging systems is that it they are projection based such that depth information is lost. As a result, true three-dimensional location of objects such as an elongate instrument in the field of view of the fluoroscope is lost as a result of generating a two-dimensional fluoroscopic image. Thus, even if it is possible to obtain accurate x-y or two-dimensional data, it may be difficult or impossible to accurately determine the location of a catheter in three-dimensional space. Examples of fluoroscopy instruments and associated methods are described in further detail in U.S. application Ser. No. 11/637,951, the contents of which were previously incorporated by reference.
In the example illustrated in FIG. 1, the shapes of the representation 12 and image 14 are generally consistent, but in some applications, the position and/or shape of a catheter or elongate instrument may differ and inaccurately reflect the shape and/or position of the instrument, which may result in complications during surgical procedures. Such mismatches may be interpreted as a problem associated with the kinematics model or controls or sensing algorithms, or as a result of contact between the subject instrument and a nearby object, such as tissue or another instrument.
A process called “registration” may be performed to spatially associate the two coordinate systems in three dimensions. Registration involves moving the elongate instrument to one or more positions, imaging the instrument with one or more positions of the fluoroscopic imaging device (e.g., the C-arm), and analyzing the images to deduce the coordinate system of the elongate instrument in relation to the coordinate system of the fluoroscopic imaging device. This process, however, an be tedious, and it is relatively easy for the elongate instrument to go out of alignment relative to the other pertinent coordinate systems.